Denicotinization of tobacco



Nov. 12, 1963 A. LENDVAI DENICOTINIZATION OF TOBACCO Filed July 27, 1960 INVENTOR. #402! W Z IYOW/ United States Patent 3,110,315 DENICQTENIZATIQN 0F TOBACCG Andrew Lend /2i, Spring Valley, N.Y. (31 Seton Hall Drive, Oakland, NJ.) Filed duly 27, Edit, Ser. No. 45,696 12 Claims. (Cl. 131-10) The present invention relates to the denicotinization of tobacco and more particularly to a method of treating nicotine-containing materials such as tobacco, tobacco smoke or tobacco extract, to a composition of matter particularly useful in the treatrnent of such materials, particularly nicotine-containing smoke and extracts originating from tobacco, and also to certain devices by means of which such treatment can be carried out in an advantageous manner.

The removal of harmful or potentially harmful constituents from tobacco smoke has been the subject of extensive research efforts. Initially, interest centered in the removal of nicotin, however, more recently, the desirability of removing not only nicotin but also tar like substances from tobacco smoke became more and more apparent.

Generally, it has been attempted to either bind or destroy tobacco smoke constituents which are considered harmful by passing the smoke through a suitably treated filter or by incorporating in the tobacco certain substances which are expected to reduce the nicotin and/ or tar content of the smoke formed upon burning of the tobacco.

However, notwithstanding the great edorts made up to now, at best only limited, partial solutions to the problem of eliminating or substantially reducing the amount of harmful constituents in tobacco smoke have been found. This is particularly so if the further requirement is added, namely that the taste and aroma of the thus treated tobacco smoke should remain substantially unimpaired.

It is therefore an object of the present invention to provide improved means for producing tobacco smoke free of all or some of its original harmful constituents or containing only substantially reduced quantities of the same.

It is another object of the present invention to provide a method for at least the partial removal of nicotin from tobacco smoke and tobacco extracts.

It is a further object of the present invention to provide a method for the removal of tar-like substances from tobacco smoke.

it is still another object of the present invention to provide a filter element which will eifectively reduce the content of harmful substances such as nicotine and tar of tobacco smoke passing through such filter element.

it is yet a further object of the present invention to provide a composition of matter and a method of making the same which composition when properly applied will be capable of removing at least a substantial portion of such harmful or potentially harmful substances from tobacco smoke.

Other objects and advantages of the present invention will become apparent from a further reading of the description and of the appended claims.

With the above and other objects in view, the present invention con-templates a method of treating tobacco smoke to reduce the proportion of harmful components therein which comprises contacting the smoke with tannic acid.

The present invention also includes a method of removing nicotine from solutions containing the same comprising the steps of forming a mixture of a nicotin-containing solution and tannic acid so as to precipitate at least a portion of the nicotin of the solution, and separating the thus formed precipitate from the remainder of the mixture.

it is furthermore within the scope of the present invention to provide as an article of manufacture, a cigarette having a porous smoke filter associated with one end thereof, at least a portion of the filter containing tannic acid.

in addition, the present invention comprises as a new composition of matter, the tannic acid ester of polyhydroxy alcohol.

Thus, according to the present invention, tobacco smoke may be treated by being contacted with tannic acid since, surprisingly, it has been found that tannic acid will react with the nicotin contained in the tobacco smoke under formation of a precipitate. For instance, when a cigarette filter is treated with a tannic acid solution and preferably also with a suitable humeotant, the nicotin contained in tobacco smoke passing through such filter will be precipitated and retained in the filter so that smoke substantially free of nicotin or containing only a greatly reduced proportion thereof will emanate from the filter.

The reaction between tannic acid and nicotine will result in formation of a nicotine-containing precipitate while simultaneously glucose will be freed from the split tannic acid molecule. The thus-formed glucose is capable of retaining pyridine formed during combustion of tobacco and thus will at least reduce the pyridine content of the smoke.

The present invention is not particularly concerned with the specific structural details of filters such as cigarette filters or other filters which may be impregnated with tannic acid and/or other tobacco smoke purifying agents which will be described in detail further below. With respect to such filters and the specific manner of impregnating the same, for instance, with solutions of the active ingredients of the present invention and subsequent removal of excess solvent, reference is made to the extensive prior art dealing with the structure of filters and the methods of impregnating the same, for instance German Patent Nos. 634,357 and 693,563, and Swiss Patent 319,926.

It has been found that according to the present invention, the nicotin content of tobacco extracts can be substantially eliminated or at least greatly reduced by adding tannic acid to such tobacco extracts and thereby causing a reaction resulting in the precipitation of nicotin under freeing of glucose from the tannic acid.

The quantity of tannic acid required to precipitate a given quantity of nicotin will depend on the molecular structure and weights of the specific reactants and will approximate about 35 parts by weight of tannic acid for the precipitation of one part by weight of nicotin.

The term tannic acid is used herein broadly, so as to include the various types of esters of gallic acids with glucose. Reference is made in this connection to the U.S. Pharmacopeia XV and the description of tannic acid contained therein.

Due to the fact that the nicotin content of tobacco varies and the effectiveness of the tannic acid depends on its variable chemical composition, it is desirable to determine experimentally for each lot of tobacco the amount of tannic acid that will be required to reduce the nicotin content of the smoke or extract to the esired extent.

Preferably, a measured quantity of the tobacco is treated as in actual consumption, for instance by smoking the cigarette, cigar or pipe in a suitable laboratory device, and the smoke (or tobacco extract if treatment of an extract is contemplated) is then contacted with a tannic acid solution of known concentration. This titration method basically consists in titrating a nicotin-containing solution with a tannic acid solution of known concentration, whereby the endpoint is reached when the last drop of tannic acid solution which is added does no longer cause precipitation of nicotin.

When tannic acid is to be incorporated into a tobacco smoke filter, it has been found desirable to incorporate therein also a humectant in order to improve contact between the tannic acid and the tobacco smoke, and also in order to facilitate retention of precipitated nicotin in the filter. As humectants may be used for instance magnesiurn chloride, calcium chloride, maleic acid or lactic acid, or polyhydroxy alcohols such as propaneand butanediols or glycerol, or detergent oils such as certain fatty alcohol sulfonates or esters of polyglycerols and esters of polyglycols known per se primarily as emulsifiers.

A cigarette filter may be treated, for instance, with an aqueous solution containing 35% tannic acid and 5% calcium chloride. Since the nicotin content of cigarettes rarely exceeds mg. per cigarette and in fact in most cases seems to be closer to about 3 mg, the aqueous solution absorbed by a single cigarette filter should contain between about 100 and 350 mg. tannic acid, preferably in most cases between 200 and 300 mg., in order to perrnit substantially complete precipitation or at least precipitation of the major portion of the nicotin contained in the cigarette smoke. Thus, the total weight of the 35% tannic acid solution which is to be absorbed by one filter in such cases will be about between 500- and 1000 mg. The filter is then dried in a manner known per se to about its moisture equilibrium under atmospheric condictions. Generally, it will not be practical to impregnate the filter with tannic acid solutions containing less than 0.5% or more than 60% tannic acid. Concentrations of between and 60% give good results and a tannic acid concentration of about 35% in the impregnating solution has frequently been found to be the most desirable concentration.

The concentration of tannic acid in the aqueous solution with which the filter is to be impregnated will be so chosen that the desired quantity of tannic acid, for instance 300 mg, will be dissolved in a quantity of water sufficiently small to be' absorbed by the filter. Thus, if the dry weight of the filter is 0.5 g. and the absorptive capacity of the filter is better than 200%, 1 g. of a 30% aqueous tannic acid solution could be applied to the filter and -will result in the incorporation of 300 mg. of tannic acid therein. Preferably, the concentration of the tannic acid in the aqueous solution will be between about 15 and 60% and most preferably between 25 and 40% Tannic acid can be incorporated in the filter in various ways, for instance, absorbing paper sheets which subsequently are to be rolled into filters, may be sprayed with a solution of a suitable humectant, such as calcium chloride, magnesium chloride, lactic acid, or malic acid, and thereafter tannin powder is dusted onto the thus moistened sheet. Finally, the thus treated sheets are fashioned into filters.

It is, of course, also possible to spray onto the filter paper a solution of tannic acid and thereafter to roll and dry the thus treated filter'paper.

Finally, good results are also obtained by first forming the filter roll or the like of suitable paper, foam plastic, or the like, and then to immerse the filter once or several times in a tannic acid solution of desired concentration.

Excess tannic acid solution which may have been absorbed V by the filter can be removed in manners known per se,

for instance by centrifuging.

According to the present invention, tar-like substances will be removed from tobacco smoke by contact with the reaction product obtained by heating a mixture of tannic acid and a liquid polyhydroxy alcohol to a temperature above the boiling point of water, preferably to the boiling point of the mixture. Thereby, apparently, esters are formed of the polyhydroxy alcohol and the tannic acid, the' degree of esterification depending to a great extent on the quantitative relationship between tannic acid and polyhydroxy alcohol.

The thus obtained reaction product which herein will be broadly called tannic acid esters of polyhydroxy alcohols can be produced, for instance, in the following manner.

EXAMPLE I 50 g. of glycerol are heated to about 70 C. and thereafter 25 g. tannic acid are stirred into the heated glycerol preferably in several smaller portions. After thorough stirring, the mixture is heated to boiling and allowed to boil until the initially cloudy mixture becomes clear and transparent. This is usually accomplished within 5-10 min. Thereafter, the mixture is allowed to cool.

Since it is usually desirable to remove not. only tar-like substances but simultaneously nicotin from the tobacco smoke, the thus formed water-soluble clear solution is then mixed with cm. of 30% aqueous tannic acid solution and, in this manner, a solution having a total tannic acid content of 370 mg./cm. is obtained, whereby the major portion of the tannic acid is free and a smaller portion thereof is esterified with the glycerol. The tannic acid ester of the polyhydroxy alcohol which forms part of this solution will obviate the need for add-' ing a separate humectant.

A cigarette filter or the like is then impregnated with the above-described aqueous solution of tannic acid and tannic acid ester of glycerol and after drying the filter so as to remove excess water, the same will be capable of effectively removing tar-like substances and nicotin from tobacco smoke passing therethrough.

impregnation of the filter may be carried out by immersing the same in the above solution which has been suitably heated to reduce its viscosity. Excess solution is removed from the filter by centrifuging. It is also possi ble to spray the above warm solution onto filter paper sheets such as porous crepe paper and thereafter to produce filters from the thus-treated paper.

EXAMPLE II 50 g. of 1-2-propylene glycol are heated to 70 C. and 20 g. of tannic acid are successively stirred into the liquid, which is further heated to boiling and allowed to boil until the initially cloudy liquid has become clear and transparent. Thereafter, the liquid is allowed to cool and is then mixed with 100 cm. of a 35% tannic acid solution.

EXAMPLE HI A mixture of 20 g. glycerol, 25 g. propylene glycol and 5 g. sorbit are heated to between 60 and 70 C. and thereafter 35 g. tannic acid are introduced in several smaller portions. The mixture is then further heated until a clear, transparent solution is formed. After cooling, 100 cm. of 50% aqueous tannic acid solution are added under stirring so that a homogeneous mixture is formed which will contain about 530 mg. of tannic acid per cm.

Preferably, glycerol or propylene glycol will be used as the polyhydroxy alcohols which are to be esterified with tannic acid, since these two polyhydroxy alcohols are generally accepted as additives and solvents for food and drug products. Other suitable polyhydroxy alcohols include trimethylene glycol, pinacol, dipropylene glycol, methyl glycerole, dextrose, levulose, arabitol, dulcitol, iditol and talitol.

The tannic acid with which the polyhydroxy alcohol is to be esterified may be any type of tannic acid, for instance, Turkish tannic acid or Chinese tannic acid. The type of tannic acid used as well as the proportionate amount of the same will manifest itself only inthe relative number of digallic acid molecules which are esterified with the glucose of the tannic acid. It has been found may be esterified with the polyhydroxy alcohol and lesser relative amounts of tannic acid will result in a lesser proportion of esterified digallic acid molecules.

As a general method of esterifying polyhydroxy alcohols with tannic acid the following procedure has given good results.

In a suitable glass vessel, one part of the polyhydroxy alcohol, such as glycerol, propylene glycol or other gly cols such as glycol, ethylene glycol or butylene glycols, or other polyhydroxy alcohols such as erythritol, pentaerythritol, sorbitol or mannitol, is heated until the viscosity of the liquid is markedly reduced, which frequently will be the case at a temperature of about 60 or 70 C. Thereafter, up to 1 /2 parts by weight of tannic acid are added either successively or in several small portions and under constant stirring the mixture is further heated to boiling. It will be observed that the liquid becomes cloudy upon introduction of the tannic acid (since the quantity of tannic acid introduced exceeds the proportion thereof which is soluble in the polyhydroxy alcohol at temperatures such as 70).

However, after boiling for between about 5 and minutes, the cloudy liquid will become clear and after cooling a fat-like dark mass will be obtained which, however, is completely miscible with water.

The thus obatined tannic acid polyhydroxy alcohol ester product can then be mixed with the desired quantity of an aqueous tannic acid solution of desired concentration and the mixture obtained thereby is then suitable for it pregnating the filter through which the tobacco smoke has to pass, in order to impede the passage of nicotin and tar-like substances therethrough.

Furthermore, it is also within the scope of the present invention to impregnate the smoking tobacco with tannic acid or tannic acid polyhydroxy alcohol esters or mixtures of the same. In other Words, while the invention is described herein primarily in connection with a filter through which the tobacco smoke passes, the substances which according to the present invention are incorporated in the filter may also be incorporated directly in the tobacco which is to be smoked and surprisingly it has been found that the tar and nicotine content of the smoke reaching the mouth of the smoker will be greatly reduced in this manner.

It has also been found that the quantity of harmful ingredients in the mainstream of the tobacco smoke (i.e. in the smoke stream destined to reach the mouth of the smoker) will be reduced by adding to the tobacco certain agents of a probably catalytic name, such as oxalic acid and/ or esters of oxalic acid, such as diethyl oxalate, etc. or such carbohydrates which are precursors of oxalic acid, in order to decrease the quantity of nicotin in the main stream of smoke. As an acid, oxalic acid might bind nicotin and advance the burning and degradation of it, and thus also less tar will be produced.

It is also within the scope of the present invention to treat nicotin-containing tobacco extracts with tannic acid, whereby the nicotin will be precipitated and upon separation of the nicotin a substantially nicotin-free tobacco extract may be formed.

The thus produced nicotin-free tobacco extract may then be used for impregnating cigarette filters and the like in order to enhance the taste and aroma of the tobacco smoke passing through such filter. It is also within the scope of the present invention to impregnate the filter with a tobacco extract to which other flavoring agents have been added, such as the flavoring agents which frequently are added to the tobacco, for instance, vanilline, coumarine, peppermint, camomile, and the like.

It has been found particularly advantageous to form an extract of the type of tobacco which will be used for the manufacture of the respective filter cigarette, to denicotinize the extract in acordance with the present invention and to impregnate the filter with tannic acid and a tannic acid ester or a polyhydroxy alcohol dissolved in the thus formed denicotinized extract. Thereby it is achieved that the additional flavoring or aromatization of the tobacco smoke passing through the filter will correspond to the fiavor and taste of the tobacco of the respective filter cigarette.

It is, of course, also possible, in accordance with the present invention, to extract tobacco, to remove nicotin from the thus formed extract and to incorporate the nicotin-free extract in the previously extracted tobacco so that the same will have substantially its original taste and aroma, while being free of substantially all or at least part of its original nicotin content. The degree to which nicotin is removed from the tobacco extract by treatment with tannic acid depends on the specific treating conditions and by using a s-ufiicient proportion of tannic acid, it is possible to produce a tobacco extract which is substantially completely free of nicotin.

Furthermore, it has also been found to be advantageous to treat the filter of the cigarette or the like with the denicotinize/l tobacco solution. In this manner a filter is obtained which more or less simulates for the smoker a filterless cigarette, the treated filter taking the place of the tobacco in the end portion of a filterless cigarette which is held in the mouth of the smoker.

As has been described further above, an impregnating solution for incorporation in cigarette filters or the like can be produced which consists of tannic acid esters of polyhydroxy alcohols and an aqueous tannic acid solution. Thereby the tannic acid esters of the polyhydroxy alcohols will primarily serve to remove tanlike substances from the smoke, while the free tannic acid will precipitate nicotin. It is also with n the scope of the present invention to dissolve tannic acid and/ or the ester of a polyhydroxy alcohol in a de-nicotinized tobacco extract, rather than in water, and use the thus-formed solution as the impregnating liquid for impregnating the tobacco smoke filter. In this mariner the filter will irnpar-t tobacco flavor to the smoke while removing nicotine land/or tar-like substances from the same. Of course, other flavoring agents, such as couniarin, vanillin, lemon or orange oil, peppermint, etc. also may be incorporated in the impregnating liquid.

In order to enhance the characteristic aroma of the smoke of a specific kind of cigarette, it has been found advantageous to treat the filter for such cigarette with an impregnating solution consisting of the tannic acid ester of a polyhydroxy alcohol and of a solution of tannic acid in a tobacco extract which has been made from tobacco of the same type as contained in the specific cigarette and from which nicotin has been removed by precipitation with tannic acid.

The present invention also contemplates, as an article of manufacture, a cigarette having a porous smoke filter associated with one end thereof, wherein at least a portion of the filter contains tannic acid, as well as a porous filter element adapted for the passage of tobacco smoke therethrough and impregnated with either tannic acid or a tannic acid ester of a polyhydroxy alcohol, or both. Such filters are illustrated in the drawing, wherein: I

FIG. 1 is a longitudinal section through a filter type cigarette, according to the present invention; and

FIG. 2 is a longitudinal section through a cigarette and a cigarette holder wherein the filter element is disposed in the cigarette holder.

Referring now to the drawing, and particularly to FIG. 1, a typical cigarette is shown comprising a cylindrical body of tobacco 1, Wrapped in cigarette paper 2 and having secured to one end thereof filter element 3, comprising a cylindrical reinforcing paper 4 and a porous absorbent filter body 5, impregnated with the effective ingredients of the present invention, i.e. tannic acid and a tannic acid ester of a polyhydroxy alcohol, such as propylene glycol.

In FIG. 2, reference numeral 11 indicates a cigarette without a filter which is removably inserted into a filter '2? tip 12. In the intermediate portion of filter tip 12, be tween the mouthpiece 13 and the cigarette holding portion 14, a porous absorbent filter element 15 is inserted which again is treated with the effective substances according to the present invention.

Filter elements 3 and 15 have beenillustrated as an impregnated porous body by way of example only. The filter element, of course, may be of any other type, such as fibrous material, absorbent paper or any other structure which may be impregnated with, or hold the effective ingredients of the present invention, and through which tobacco smoke may pass.

It is also within the scope of the present invention to incorporate the active ingredients, particularly tannic acid into the raw material from which the filter element is produced. Thus, it is possible to add a tannic acid solution to the paper pulp from which the filter-forming paper will be produced. In the case of foam plastic filters, the tannic acid may be incorporated into the mass prior to foaming of the same, or tannic acid may be deposited on the foamed plastic by impregnating with a tannic [acid solution and subsequent drying.

The following examples are given as illustrative only, the invention, however, not being limited to specific details of the examples.

EXAMPLE IV Impregntltion of Tobacco With THINZI'C Acid Solution 100 g. of finely cut tobacco are spread out on a screen and sprayed with a solution of 30 g. of tannic acid in 68 g. of either water or denicoitinized tobacco extract, plus 2 g. of a polyhydroxy alcohol such as 1-2 propanediol or glycerol.

After thus thoroughly and evenly wetting the tobacco, warm air is passed from below through the screen and the wet tobacco thereon until the moisture content of the thus treated tobacco has been reduced to the desired value. a

The process described herein as a laboratory experiment lends itself easily to continuous large-scale execution for instance by passing the tobacco on a conveyor through the spraying area and thereafter drying the tobacco in conventional manner.

EXAMPLE V impregnating Tobacco With a Solution of Tan nic Acid and 0f the T annic Acid Ester of a Polylzydroxy Alcohol Finely cut tobacco is impregnated on an industrial scale with the solution produced according to Example I, by spraying a portion of the solution onto a thin layer of tobacco, passing the thus wetted tobacco through a drying chamber and spraying additional solution onto the tobacco leaving the drying chamber. This can also be carried out in a drying tower wherein tobacco moving upwardly in the tower while being dried is caused to drop from the upper portion :of the tower to the bottom thereof, is sprayed with additional solution and then passes again upwardly through the tower.

'In'this manner, a particularly even distribution of the impregnating substances in the tobacco will be achieved. The total quantity of the solution, according to Example I, which is applied to the tobacco, approximately equals the dryweight of the untreated tobacco.

EXAMPLE VI Production of Denicotinized T obtzcco Extract g. of tobacco are distributed in between 50 and 100 cubic centimeters of water, or preferably a slightly acidified water such as a 1/20 normal sulfuric acid solution. The thus formed suspension is heatedto boiling and thereafter allowed to stand at close to boiling temperature for a period of between 10 and 30 minutes. Thereafter, the thus formed extract solution is separated from the tobacco residue, for instance, by centrifuging. The nicotin content of the extract solution is then determined by titration with a tannic acid solution of known concentration. The end point is reached when upon addition of tannic acid solution no further precipitation takes place.

A control determination will show that upon reaching of the above-described end point no further nicotin precipitation will occur upon the addition of picric acid.

After determining in this manner the amount of tannic acid solution required for denicotinization of the extract, the foregoing is repeated on a desired larger scale.

For instance, assuming that 6.2 g. tannic acid were required to precipitate all of the nicotin of the above described extract solution form of 10 g. of tobacco, it is now possible to extract for instance 100 kg. of tobacco and. to treat the extract solution with a tannic acid solution containing 62 kg. of tannic acid.

After removal of the precipitate formed by treating of the extract solution with tannic acid, a nicotin-free extract solution is obtained which may be incorporated in the previously extracted tobacco, or may be incorporated, for instance, into the filter portion of cigarettes, etc. to give to such portions a tobacco-like taste and aroma. It is also possible to concentrate the denicotinized tobacco solution prior to making further use of the same.

The tannic acid solution which is to be used for denicotinizing the tobacco extract may be a pure aqueous solution or any other type of suitable tannic acid solution, for instance, a solution of tannic acid in previously denicotinized tobacco extract.

EXAMPLE VII Solution for Impregnating Filler Elements 10 kg. glycerol, 30 kg. 1-2 propanediol and 5 kg. sorbitol are mixed and heated to C. Upon reaching this temperature, 35 kg. tannin are stirred into the mixture which is then further heated, preferably under stirring, until a clear, transparent solution is formed. Thereafter, liters of a 50% solution of tannin in denicotinized tobacco extract are added and thoroughly mixed with the previously formed transparent solution to form the impregnating solution.

. Crepe paper, which is to be used for a cigarette filter, is then sprayed with the above described impregnating solution and dried prior to being fashioned into filter elements.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications Without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention, and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. The method of treating tobacco smoke to reduce the proportion of harmful components therein which comprises contacting tobacco smoke with the tannic acid ester of a polyhydroxy alcohol formed of between 40 and parts by weight of tannic acid and-100 parts by weight of a polyhydroxy alcohol. Q

2. The method of treating tobacco smoke to reduce the proportion of harmful components therein which comprises passing tobacco smoke through a porous smoke filter impregnated with a tannic acid ester of a polyhydroxy alcohol.

3. The method of treating tobacco smoke to reduce the proportion of harmful components therein which comprises passing tobacco smoke through a porous smoke filter impregnated with tannic acid and tannic acid ester of a polyhydroxy alcohol.

4. ,The method of treating tobacco smoke to reduce the roportion of harmful components therein which cornprises passing tobacco smoke through a porous smoke filter impregnated with tannic acid and the ester of tarmic acid with a polyhydroxy alcohol selected from the group consisting of ethylene glycol, propylene glycol, butylene glycol, tri-methylene glycol, pinacol, dipropylene glycol, glycerol, methyl-glycerol, erythritol and isomers thereof, dextrose, levulose, arabitol, sorbitol, mannitol, dulcitol, iditol and talitol.

5. The method of treating tobacco smoke to reduce the proportion of harmful components therein which comprises contacting the smoke with a polyhydroxy alcohol which has been at least partially esterified with tannic acid.

6. The method of treating tobacco smoke to reduce the proportion of harmful components therein which comprises passing tobacco smoke through a porous smoke filter impregnated with an aqueous solution of tannic acid and of a tannic acid ester of a polyhydroxy alcohol.

7. As an article of manufacture, a cigarette having a porous smoke filter associated with one end thereof, at least a portion of said filter containing tannic acid and the tannic acid ester of a polyhydroxy alcohol.

8. As an article of manufacture, a cigarette having a porous smoke filter associated with one end thereof, at least a portion of said filter containing a tannic acid ester of a polyhydroxy alcohol.

9. As an article of manufacture, a cigarette having a porous smoke filter associated with one end thereof, at least a portion of said filter containing tannic acid and a polyhydroxy alcohol which has been at least partially esterified with tannic acid.

10. As an article of manufacture, a porous filter element adapted for the passage of tobacco smoke therethrough and being impregnated with tannic acid and the tannic acid ester of a polyhydroxy alcohol.

11. As an article of manufacture, a porous filter element adapted for the passage of tobacco smoke therethrough and being impregnated with a polyhydroxy alcohol which has been at least partially esterified with tannic acid.

12. As an article of manufacture, a porous absorbent filter element adapted for the passage of tobacco smoke therethrough and for the treatment of said tobacco smoke during said passage, said filter containing as a flavoring agent substantially nicotin-free tobacco extractives and also containing tannic acid and a tannic acid ester of a polyhydroxy alcohol in an amount effective for the treatment of the tobacco smoke passing therethrough, whereby the amount of nicotin in smoke passing through said filter will be reduced by contact of said smoke with said tannic acid and the amount of tar substances will be reduced by contact with said tannic acid ester of a polyhydroxy alcohol.

References Cited in the file of this patent UNITED STATES PATENTS 134,713 Turner Ian. 7, 1873 740,283 Klenk Sept. 29, 1903 757,514 Thorns Apr. 15, 1904 802,487 Wimmer Oct. 14, 1905 2,108,860 Kaufiman Feb. 22, 1938 2,162,738 McCoy June 20, 1939 2,478,473 Eskew Aug. 22, 1947 2,582,075 Severi Jan. 8, 1952 FOREIGN PATENTS 173,262 Austria Dec. 10, 1952 755,479 Great Britain Aug. 22, 1956 541,337 Italy Mar. 28, 19 56 

1. THE METHOD OF TREATING TOBACCO SMOKE TO REDUCE THE PROPORTION OF HARMFUL COMPONENTS THEREIN WHICH COMPRISES CONTACTING TOBACCO SMOKE WITH THE TANNIC ACID ESTER 